Queues, PubSub & Background

When to use

• Decoupling producers/consumers with backpressure

• Broadcasting events to multiple subscribers

• Running background loops with graceful shutdown

Queue (bounded)

import { Queue } from "effect" const q = yield* Queue.bounded<string>(32) yield* Queue.offer(q, "job") const job = yield* Queue.take(q)

PubSub (broadcast)

import { PubSub } from "effect" const ps = yield* PubSub.bounded<string>(32) yield* PubSub.publish(ps, "evt")

Background Fiber

const fiber = yield* Effect.fork(loop) yield* Fiber.interrupt(fiber)

Guidance

• Prefer bounded queues to apply natural backpressure

• Use multiple workers by forking consumers

• Ensure background fibers are interrupted during shutdown

Pitfalls

• Unbounded queues lead to memory growth

• Silent background failures → add logging/metrics

Cross-links

• Concurrency for pools and interruption

• Time/Logging for observability of background tasks

Local Source Reference

CRITICAL: Search local Effect source before implementing

The full Effect source code is available at docs/effect-source/ . Always search the actual implementation before writing Effect code.

Key Source Files

• Queue: docs/effect-source/effect/src/Queue.ts

• PubSub: docs/effect-source/effect/src/PubSub.ts

• Fiber: docs/effect-source/effect/src/Fiber.ts

Example Searches

Find Queue patterns

grep -F "bounded" docs/effect-source/effect/src/Queue.ts grep -F "offer" docs/effect-source/effect/src/Queue.ts grep -F "take" docs/effect-source/effect/src/Queue.ts

Study PubSub operations

grep -F "publish" docs/effect-source/effect/src/PubSub.ts grep -F "subscribe" docs/effect-source/effect/src/PubSub.ts

Find background fiber patterns

grep -F "fork" docs/effect-source/effect/src/Fiber.ts grep -F "interrupt" docs/effect-source/effect/src/Fiber.ts

Look at Queue test examples

grep -F "Queue." docs/effect-source/effect/test/Queue.test.ts

Workflow

• Identify the Queue or PubSub API you need

• Search docs/effect-source/effect/src/Queue.ts or PubSub.ts for the implementation

• Study the types and backpressure patterns

• Look at test files for usage examples

• Write your code based on real implementations

Real source code > documentation > assumptions

References

• Agent Skills overview: https://www.anthropic.com/news/skills

• Skills guide: https://docs.claude.com/en/docs/claude-code/skills